Button terminal
Japanese arcade buttons, unlike European and American buttons, use 0.110"/2.8mm pins. 2.8mm terminals can easily be found outside Japan. The original terminals are open barrel crimps, with a plastic sleeve to snap around it.
Sanwa
Terminals are called AT-110.
Sleeves are called SR-110.
PRO-TIP: Don't attach the sleeves until you have tested the harness you're making; they can be difficult to remove.
PRO-TIP: Without sleeves you can get away without buying buttons, simply touch one terminal to another to simulate a button press. For games with autofire this can be very useful for the gamer on a budget.
How they look
Where to get them
https://www.arcadepartsandrepair.com/product-category/connectors-sockets-pins/quick-disconnects/
2.8mm Terminals and Covers from PoleVolt, UK delivery only